Plasma is an ionized gas called a fourth state of matter, the other states being solid, liquid, and gas. Plasma is composed of ions, neutrons, and electrons that are at a normal or activated state. Plasma is an electrically neutral medium from a macroscopic viewpoint. However, since plasma includes free charged-holes, plasma can be electrically conductive.
When gas is subject to strong energy, electrons are separated from atoms or molecules, resulting in plasma in which electrons and positive ions are present in a mixture. Plasma is a highly reactive medium having high redox reactivity. Plasma may be in a high temperature environment or a low temperature environment according to methods by which particles are activated and operation energy used to generate the plasma. Plasma with a high temperature environment is called high temperature plasma and plasma with a low temperature environment is called low temperature plasma. Due to this broad temperature range of plasma, plasma technologies are applicable in various fields such as surface coating, gas treatment, waste removal, chemical redox reaction, synthesis of novel materials, and mechanical work.
In water treatment, conventional methods involve use of an expensive filter system, ozone, or ultraviolet rays all of which are expensive methods, or chemicals such as chlorine, which is an inexpensive method.
For example, in the case of treatment of ballast water, when ballast water is introduced into or pumped out of ships, hazardous aquatic life or marine creatures in seawater move in and out of the ship. In order to prevent a marine ecosystem from being destroyed by foreign marine creatures that move along ballast water in ships moving from one country to another, ballast water treatment technologies that are currently being used mainly include electrolysis, ozone treatment, ultraviolet-ray sterilization, and electrolysis. However, these methods require expensive equipment, strong energy, and high power consumption.
When sanitizing swimming pool water, the water is usually sanitized with a circulation filter and chlorine. For this, chlorine is normally fed three or four times a day and a circulation filtering process is performed. For the form of chlorine used for chlorine disinfection, a chlorine gas is used for large swimming pools and hypo sodium chlorite is used for small swimming pools. Chlorine feeding is advantageous in terms of perfect sterilization effect and easy water treatment for a large volume of water at a single time. However, it is disadvantageous in that feeding has to be performed every four hours due to low solubility of chlorine in water.
Furthermore, this water treatment technology involving underwater chlorine feeding has side effects such as environmental pollution and negative effects on human bodies when high doses of chlorine are used. In terms of other treatment methods, ozone-based treatment is problematic in terms of low cost efficiency due to installation costs and operation costs, and ultraviolet-ray treatment technology is disadvantageous in terms of frequent replacements of lamps, reduction in effective period and valid irradiation distance of lamps attributable to adhesion of polysaccharides to the surface of a quartz tube of lamps, leakage of a wavelength source material sealed in a quartz tube attributable to tube breaking, and toxicity of a wavelength source material that is leaked from a quartz tube.
In addition, there is disclosed a water treatment apparatus and method using low temperature plasma. This technology is disadvantageous in that it requires a bubble generating device used to change a pure liquid state to a state in which liquid and gas are mixed. This results in a large size of equipment, requiring a large installation space. Due to spatial constraints, water treatment using low temperature plasma used only in limited areas.